Device for clamping the trailing end portion of a sheet to a drum

ABSTRACT

A device comprising clamp means including hooks for piercing the trailing end portion of a sheet after the leading end portion of the sheet is automatically gripped by grip claw means on a rotating drum and the sheet is wound on the drum. By being pierced by the hooks, the trailing end portion of the sheet is automatically clamped to the periphery of the drum.

United States Patent [191 Murata 1 Jan. 7, 1975 DEVICE FOR CLAMPING THE TRAILlNG END PORTION OF A SHEET TO A DRUM [75] inventor: Keisuke Murata, Tokyo, Japan [73] Assignee: Ricoh Co., Ltd., Tokyo, Japan [22] Filed: July 27, 1973 [21] Appl. No.: 383,158

[30] Foreign Application Priority Data Aug. 8, 1972 Japan 47-79257 [52] U.S. Cl. 101/415.1 [51] Int. Cl B411 27/06 [58] Field of Search 101/415.1,132,132.5, 101/142-144, 409-411 [56] References Cited UNITED STATES PATENTS 2,021,894 11/1935 Morse 101/415.1

3,490,367 1/1970 Kaneko et a1 101/144 3,664,260 5/1972 Miller 101/132 3,731,624 5/1973 Kaneko l0l/142 Primary Examiner-J. Reed Fisher Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran [57] ABSTRACT A device comprising clamp means including hooks for piercing the trailing end portion of a sheet after the leading end portion of the sheet is automatically gripped by grip claw means on a rotating drum and the sheet is wound on the drum. By being pierced by the hooks, the trailing end portion of the sheet is automatically clamped to the periphery of the drum.

6 Claims, 6 Drawing Figures Patented Jan. 7, 1975 3,858,513

4 Sheets-Sheet 1 Pa tented Jan. 7, 1975 4 Sheets-Sheet 2 FIG.2

Patented Jan. 7, 1975 4 Sheets-Sheet 5 FIG.3

Patented Jan. 7, 1975 3,858,513

4 Sheets-Sheet 4 DEVICE FOR CLAMPING THE TRAILING END PORTION OF A SHEET TO A DRUM BACKGROUND OF THE INVENTION This invention relates to a device for automatically clamping the trailing end portion of a sheet to a rotating drum by piercing it with hooks after the leading end portion of the sheet is automatically gripped by grip claw means on the drum.

In apparatus comprising a drum adapted to be rotated to perform an operation with a sheet mounted on the surface thereof and having its leading end portion automatically gripped by one portion of the drum, it is necessary to positively clamp not only the leading end portion of the sheet but also the trailing end portion thereof to the periphery of the drum.

In offset duplicating apparatus, for example, a sheet, such as a master or printing plate, is supplied to a rotating drum (or master cylinder) and its leading end portion is clamped to the periphery of the master cylinder by being gripped by grip claw means provided on the master cylinder. In some types of offset duplicating apparatus, the trailing end portion of the master plate is not clamped to the master cylnder and thus free to move. The master plate having a free trailing end portion has the disadvantage of frequently being inadvertently brought into contact with the ink roller and soiled with ink.

In some types of duplicating apparatus, means is pro vided for preparing a master plate on the periphery of a drum by mounting on the drum a photosensitive sheet used for electrophotography. If the trailing end portion of the photosensitive sheet on the drum is not clamped to the drum, it will not be possible to satisfactorily carry out exposure of the sheet to an optical image of an original. It is thus desirable to positively clamp not only the leading end portion but also the trailing end portion of the sheet to the drum.

Proposals have been made to obviate these disadvantages of the prior art by providing means to clamp the trailing end portion of a sheet to a drum. The operation of mounting a sheet on a drum can be performed either by manually clamping the leading and trailing end portions or the drum when the sheet is mounted on the drum after the rotation of the drum is interrupted, or by feeding a sheet in good timing to the rotating drum and clamping both the leading and trailing end portions thereof to the drum without interrupting its rotation.

In one method known in the art to clamp not only the leading end portion but also the trailing end portion of a sheet to a drum while the latter is rotating, the sheet automatically fed to the rotating drum has its leading end portion gripped by grip claws and clamped to the drum, and the trailing end portion thereof is clamped to the drum by clamp means disposed in a recess in the periphery of the drum which clamp means is pulled out of the recess and moved above the sheet when the sheet is fed to the drum and returned to its original position in the recess when the trailing end portion of the sheet is brought to a position in which it is engaged by the clamp means and clamped to the drum.

The method of manually clamping the sheet to the drum has the disadvantages of not only requiring troublesome manual attention but also having to interrupt the rotation of the drum. The conventional method of using clamp means to clamp the trailing end portion of the sheet to the drum is not without disadvantages. This method requires a complex mechanism for performing various operations, and difficulty is experienced in performing these operations in timed relation.

SUMMARY OF THE INVENTION This invention has as its object the provision of a device for automatically clamping the trailing end portion of a sheet to a rotating drum which obviates the disadvantages of similar devices of the prior art.

This invention permits the trailing end portion of a sheet to be automatically clamped to the periphery of a rotating drum, with the sheet being maintained in intimate contact with the periphery of the drum after'the trailing end portion thereof is clamped. Any sheet can have its trailing end portion clamped to the periphery of the drum irrespective of the length of the sheet or the presence of openings in the sheet. The clamped trailing end portion of the sheet is readily released from the periphery of the drum when the sheet is to be removed from the drum.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the device for clamping the trailing end portion'of a sheet to a drum comprising one embodiment of the invention;

FIG. 2 is a side view of a drum with certain portions thereof being cut away to show the mechanism disposed in the interior of the drum;

FIG. 3 is a plan view of FIG. 1 with the drum being eliminated in the interest of brevity;

FIG. 4 is a view showing the operation of the sheet hold-down roller; and

FIG. 5 and FIG. 6 are views showing the operation of the mechanism shown in FIG. 2.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1, a drum 1 is mounted on a shaft 2 rotatably supported at its opposite ends by a pair of side plates (one of which is shown at 3 in FIG. 3) and rotated in the direction of an arrow 4 by conventional drive means'(not shown). An actuation cam 5 is secured to the shaft 2 and tracked at its periphery by a roller 7 supported through a shaft on the lower portion of a free end of a follower 6 which is pivotally supported at its base by a shaft 8 connected to side plate 3 (See FIG. 3). The follower 6 is formed at the upper portion of its free end with a bent portion 6a which is adapted to be engaged and locked by an offset portion 9a of locking member 9. When the roller 7 of the follower 6 is in engagement with a major diameter portion 5a of the actuation cam 5, there is a gap between the offset portion 9a of the locking member 9 and the bent portion 6a of the follower. However, when the roller 7 drops out of engagement with portion 50, it is held out of engagement with a valley 5b and a minor diameter portion 5c, the bent portion 6a is brought into pressing engagement with the offset portion 9a and locked thereby.

The locking member 9 is pivotally supported at its base by a shaft 11 connected to a side plate 3 and urged to move clockwise about the shaft 11 by the biasing force of a spring 12 connected at one end to an immovable member such as a pin on plate 3 (not shown) and at the other end to the member 9. The member 9 is thus brought into pressing engagement at its back edge 9b with the lower portion of one side edge of an operation lever 13. The operaation lever 13 is pivotally supported by a shaft 14 connected to the side plate 3 and urged to move clockwise about the shaft 14 by the biasing force of a spring 15 connected at one end to another immovable member, such as a pin on plate 3 (not shown) and at the other end to the lever 13, so that the operation lever 13 is normally disposed in a position in which it is maintained at the other side edge thereof in pressing engagement with a stopper 16.

As also seen in FIG. 3, a gear 19 of a spring clutch generally designated 18 is loosely mounted at one end portion of a shaft 17 rotatably supported by the pair of side plates 3 (only one side plate is shown), and a fixed member 21 disposed adjacent the gear 19 is secured to the shaft 17 by a screw 22. A helical spring 23 is mounted on bosses of the gear 19 and fixed member I 21, and connected at one end portion 23a to the fixed member 21 and is in pressing engagement at the other end portion 23b thereof with the bent portion 6a of the follower 6. The boss of the fixed member 21 has a diameter which is slightly smaller than that of the boss of gear 19, so that the helical spring 23 is maintained in intimate contact with the boss of the gear 19 but spaced apart from the boss of the fixed member 21. when fitted over them.

The gear 19 is driven by a gear 44 to rotate clockwise in FIG. 1. However, since the one end portion 23b of the helical spring 23 is in pressing engagement with the bent portion 6a of the follower 6 and the spring 23 is loose, rotation of the gear 19 is not transmitted to the fixed member21 and the gear 19 consequently rotates idly.

A pair of support arms 24 and 25 are loosely mounted at bosses 24a and 25a thereof on the shaft 17. Cutouts 24b and 25b are formed in the support arms 24 and-25 for receiving therein pins 26 and 27 respectively which are fixed on the shaft 17 to limit the range of movement of the support arms 24 and 25. The support arms 24 and 25 are interconnected by a stay 28 and support at their free ends a sheet hold-down roller 29 for rotation. The shaft 17 supports a plurality of sets of support arms 24 and 25, so thata plurality of sheet hold-down rollers 29 are provided.

In FIG. 2, the drum 1 is shown as being formed therein with a relatively large recess 1a defined by two side walls 1b loosely supporting'opposite ends of a shaft 31 having sheet" grip claws 32 secured thereto at their base. The sheet grip claws32 each have a free end which is urged to move into pressing engagement with a front end portion 1c of the periphery of the drum 1 by the biasing force of a spring 33 mounted between the side wall 1b and the claws 32.

Clamp means 34 comprising a plurality of plate members is disposed in a rear end portion of recess 1a in the periphery of the drum 1 and secured at its base to a shaft 35 loosely supported at opposite ends by the two side walls 1b. The clamp means 34 is urged to move clockwise about the shaft 35 by the biasing force of a spring 36 connected at one end to the side wall 1b and at the other end to the clamp means 34, so that a projection 34a formed at a free end of each plate member of the clamp means 34 is maintained in pressing engagement with the front end of one of a plurality of stoppers 37 corresponding in number to the plate members of the clamp means 34. The stoppers 37 are secured at their bases to a hold plate 38 disposed parallel to the axis of the drum 1 and having at its opposite end bent portions 38a (only one of such bent portions is shown) each pivotally supported by shafts 39 connected to the side walls lb of the drum 1.

The hold plate 38 is formed. at its base with a plurality of slots (not shown) each loosely receiving therein a free end portion of one of a plurality of guide rods 49 secured at their base to a reinforcing plate 1d. A compression spring 41 is mounted between the free end of the hold plate 38 and the reinforcing plate 1d to urge the hold plate 38 to move counter clockwise about shaft 39, so that the hold, plate 38 is maintained at its base in pressing engagement with arear end portion 1e of the periphery of the drum 1.

Ahook 34b is formed at the free end of each plate member of the clamp means 34 for piercing the trailing end portion of a sheet 42 as subsequently to be described and clamping the end of the sheet to the drum. A recess 34c is formed at the free end of each plate member of the clamp means 34 for relieving the stoppers 37. When the clamp means 34 'is in the position shown in FIG. 2, the actuation cam 5 is'in the position shown in FIG. 1.

In operation as shown in FIG.2, the sheet 42 is automatically fed to the drum 1 by a known sheetfeed device (not shown). When the leading end portion of the sheet 42 reaches the recess 1a in the drum 1, the grip claws 32 are opened and closed with appropriate timing as shown in dash-and-dot lines to grip the leading end portion of the sheet 42. Clamping of the trailing end portion of the sheet 42 to the periphery of the drum 1 while the leading end portion thereof is gripped by the grip claws 32 on the rotating drum 1 can be accomplished by manually moving the operation lever 13 (See FIG. 1) to an operative position shown at 13A in dash-and-dot lines in FIG. 1.

Moving the operation lever 13 to its, operative position the bent portion 6a permits the locking member 9 to move clockwise and-if released from the bent portion 6a of the follower 6. Thus, the locking member 9 is free to move as aforementioned, and the roller 7 comes into engagement with the major diameter portion 5a of the cam 5, the engagement of the offset portion 9a with the bent portion 6a is'loosened and released. As the drum 1 and'the actuation cam 5 continue to rotate in the direction of the arrow 4, with the locking member 9 released from locking engagement with the follower 6, the roller 7 will ride on minor diameter portion 50 and is brought into engagement with the recess 5b. Thereupon, the follower 6 moves counter clockwise and the end portion 23b of the spring 23 is released from pressing engagement with the bent portion 6a of the follower 6. Although the shaft 17 is urged to move clockwise in FIG. 1 by the weight of the shaft hold-down roller 29 and the suport arms 24 and 25, its clockwise movement is precluded by the end portion 23b of the spring 23 being maintained in pressing engagement with the bent portion 6a of the follower 6 in FIG. 1. As a result, there is a relatively large gap between the spring 23 and the boss of the fixed member 21.

The operation lever 13 is held in the operative position for only a short interval so that the locking member 9 can be released from engagement with .thefollower 6. The locking mechanism will be restored to its position shown in FIG. 1 when the roller 7 is again brought into engagement with the major diameter portion 5a of the actuation cam 5.

Whe the follower 6 pivots about the shaft 8 and its forward end moves downwardly in FIG. 1, the end portion 23b of the spring 23 is released from engagement with the bent portion 6a of the follower 6. As a result, the spring 23 is tightened by its resilience and clamped over the boss of the gear 19, so that the spring 23 and the boss of the gear 19 act as a unit and rotation of the gear 19 is transmitted to the spring 23.

By the time end portion 23b of the spring 23, after from engagement with the bent portion 6a of the follower 6 substantially makes one complete revolution together with the gear 19., the follower 6 has pivoted back to its original position. Thus, the end portion 23b is brought into pressing engagement with the bent portion 6a again and further rotation of the former is precluded. As a result, the spring 23 is again loosened by the rotation of the gear 19, so that the gear 19 can rotate alone.

It will be appreciated that the spring clutch 18 performs the function of tightening the spring 23, and that it is not intended to transmit the rotation of the gear 19 directly to the fixed member 21 and the shaft 17. More specifically, when the clutch 18 is engaged, the spring 23 is tightened by its resilience and clamped over the boss of the gear 19 to act as a unit with the gear 19 and rotate therewith. However, since the end portion 23b is brought into pressing engagement with the bent portion 6a before the spring 23 is tightened by its resilience and clamped over the boss of the fixed member 21, the spring 23 is not clamped to the boss of the fixed member 21.

On the other hand, the spring 23 is tightened by the gear 19 and charged as aforementioned and produces a torsion torque which brings the sheet hold-down roller 29 connected to the fixed member 21 into pressing engagement with the periphery of the drum 1 with a light force as shown in FIG. 4, thereby forcing the sheet 42 tightly over the periphery of. the drum 1.

Further rotation of the drum 1 moves the sheet hold down roller 29 from the rear end portion 1e of the periphery of the drum 1 into engagement with the recess In as shown in FIG. 5, simultaneously as the roller 7 is brought into engagement with the valley 5b of the actuation cam 5. Thus the trailing end portion 42a of the sheet 42 is pushed by the sheet hold-down roller 29 into the recess 1a, so that the hooks 34b of the clamp means 34 penetrate the trailing end portion 42a of the sheet 42. The sheet hold-down roller 29 rotates in the direction of an arrow 43 in FIG. 6 about the shaft 17 by virtue of theaction of the spring clutch l8 and forces the trailing end portion 42a of the sheet 42 tightly against the hold plate 38, thereby permitting the trailing end portion 42a to be fully penetrated by the hooks 34b.

The hold plate 38 moves clockwise as it is pressed by the hold-down roller 29, so that the projections 34a of the clamp means 34 are released from engagement with the stopper 37. As a result, the clamp means 34 is moved clockwise by the biasing force of the spring 36 and forces the trailing end portion 42a of the sheet 42 tightly over the periphery of the drum 1. the sheet holddown roller 29 is released from engagement with the hold plate 38 as the drum 1 rotates in the direction of the arrow 43 about the shaft 17 in FIG. 6 to be restored and held in the original position shown in FIG. 1.

When it is desired to remove the sheet 42 from the drum 1, the trailing end portion 42a of the sheet 42 can be released from the hooks 34b of the clamp means 34 by merely moving the leading end portion thereof away from the periphery of the drum 1. No specific means is required for releasing the trailing end portion of the sheet from its clamped engagement with the drum. Releasing of the trailing end portion 42a of the sheet 42 from the hooks 34b moves the clamp means 34 counter clockwise about the shaft 35 and the projections 34a of the clamp means 34 are released from engagement with the stopper 37, so that the hold plate 38 is restored from its position shown in FIG. 6 to its original position shown in FIG. 2.

The invention has been described as effecting clamping of the sheet trailing end portion 42a by manually operating the operation lever 13. It is to be understood that the invention is not limited to this mode of opera tion and that the operation lever 13 may be automatically rendered operative conjointly with the actuation of the sheet feed mechanism adapted to feed the sheet 42 to the drum 1.

What is claimed is:

l. A device for clamping the trailing end portion of a sheet mounted on the peripheral surface of a rotating drum comprising:

a. clamping means disposed within an opening in the drum surface and mounted for pivoting between an inner position and an outer position, said clampling means comprising: I i. a plurality of plate members each having a free end with an adjacent recess;

ii. hook means on each of said plate members for hooking the trailing end of the sheet when brought into contact therewith; and

iii. spring means for urging said plate members toward said inner position;

b. hold-plate means disposed within said opening adjacent to said clamping means and mounted for pivoting between an inner position and an outer position, said hold-plate means comprising:

i. a pivoted hold-plate disposed adjacent said plate members in a position in which said hook means extend thereby outwardy of said opening;

ii. stop means on said hold-plate engaging the free ends of said plate members for preventing said clamping means from pivoting to its inner position; and

iii. spring means for urging said hold plate toward its outer position;

c. a shaft mounted for rotation ajacent said drum;

d. rotating means for rotating said shaft;

e. spring clutch means for operatively connecting, when engaged, said rotating means and said shaft to urge said shaft to rotate;

f. lock means for maintaining said spring clutch means disengaged;

g. sheet hold-down means mounted on said shaft for rotation therewith and including roller means thereon for pressing said sheet against the periphcry of said drum and bringing the trailing end of said sheet into contact with said hook means for hooking thereby; and

b. means responsive to the rotation of said drum for engaging said spring clutch means when said lock means is released, to urge said shaft to rotate whereby said roller means, urged to rotate with said shaft, upon bringing the trailing end of the sheet into contact with said hook means in said opening, pivots said hold-plate means to its inner 7 8 position causing the stop means thereon to enter 4. A device as in claim 3 wherein said holding means the recesses adjacent the free ends of said plate comprises: members permitting said clamping means to pivot i. a pivotable member engaging said abutment means; to its inner position drawing the trailing end porii. means for urging said pivotable member to pivot tion of said sheet into said opening and maintaining out of engagement with said abutment means; and said sheet in contact with the surface of the drum. iii. an operation lever holding said pivotable member 2. A device as in claim 1 wherein said means responfrom pivoting by said urging means. sive to the rotation of said drum comprises an actuation 5. A device as in claim 2 wherein the periphery of cam secured to one side of the drum for rotation theresaid actuation cam comprises: with and pivotable follower means for tracking the pe- 10 i. a major diameter portion; riphery of said actuation cam. ii. a minor diameter portion; and

3. A device as in claim 2 wherein said lock means iii. a valley in said minor diameter portion. comprises abutment means on said follower means en- 6. A device as in claim 1 wherein said rotating means gaged by an end of said spring clutch means and means comprises a rotating gear loosely mounted on said shaft for holding said follower means against pivoting to reand having a boss thereon.

lease said end of said spring clutch means. 

1. A device for clamping the trailing end portion of a sheet mounted on the peripheral surface of a rotating drum comprising: a. clamping means disposed within an opening in the drum surface and mounted for pivoting between an inner position and an outer position, said clampling means comprising: i. a plurality of plate members each having a free end with an adjacent recess; ii. hook means on each of said plate members for hooking the trailing end of the sheet when brought into contact therewith; and iii. spring means for urging said plate members toward said inner position; b. hold-plate means disposed within said opening adjacent to said clamping means and mounted for pivoting between an inner position and an outer position, said hold-plate means comprising: i. a pivoted hold-plate disposed adjacent said plate members in a position in which said hook means extend thereby outwardy of said opening; ii. stop means on said hold-plate engaging the free ends of said plate members for preventing said clamping means from pivoting to its inner position; and iii. spring means for urging said hold plate toward its outer position; c. a shaft mounted for rotation ajacent said drum; d. rotating means for rotating said shaft; e. spring clutch means for operatively connecting, when engaged, said rotating means and said shaft to urge said shaft to rotate; f. lock means for maintaining said spring clutch means disengaged; g. sheet hold-down means mounted on said shaft for rotation therewith and including roller means thereon for pressing said sheet against the periphery of said drum and bringing the trailing end of said sheet into contact with said hook means for hooking thereby; and h. means responsive to the rotation of said drum for engaging said spring clutch means when said lock means is released, to urge said shaft to rotate whereby said roller means, urged to rotate with said shaft, upon bringing the trailing end of the sheet into contact with said hook means in said opening, pivots said hold-plate means to its inner position causing the stop means thereon to enter the recesses adjacent the free ends of said plate members permitting said clamping means to pivot to its inner position drawing the trailing end portion of said sheet into said opening and maintaining said sheet in contact with the surface of the drum.
 2. A device as in claim 1 wherein said means responsive to the rotation of said drum comprises an actuation cam secured to one side of the drum for rotation therewith and pivotable follower means for tracking the periphery of said actuation cam.
 3. A device as in claim 2 wherein said lock means comprises abutment means on said follower means engaged by an end of said spring clutch means and means for holding said follower means against pivoting to release said end of said spring clutch means.
 4. A device as in claim 3 wherein said holding means comprises: i. a pivotable member engaging said abutment means; ii. means for urging said pivotable member to pivot out of engagement with said abutment means; and iii. an operation lever holding said pivotable member from pivoting by said urging means.
 5. A device as in claim 2 wherein the periphery of said actuation cam comprises: i. a major diameter portion; ii. a minor diameter portion; and iii. a valley in said minor diameter portion.
 6. A device as in claim 1 wherein said rotating means comprises a rotating gear loosely mounted on said shaft and having a boss thereon. 